From xtal at uic.edu Thu Apr 26 15:49:08 2018
From: xtal at uic.edu (Guggenheim, Stephen J)
Date: Thu, 26 Apr 2018 19:49:08 +0000
Subject: [Clay-talk] The new Clay Science Glossary is available at the CMS
website.
Message-ID:
The new Clay Science Glossary is available at the CMS website.
The new Glossary differs from previous versions in that a Part 1 and a Part 2 have been included: ?Part 1. General terms? and ?Part 2. Clay-related materials (excluding exchanged phases)?.
The Glossary is available in Adobe (pdf), Word (docx), and html formats. A WordPerfect format is available if requested.
Part 1 of the Glossary is a continuation of the defining of general clay terms. There are about 110 new terms defined, primarily relating to ?computer modeling? and ?geotechnical? terms.
Part 2 covers clay-related minerals, discredited names, and synonyms, but not specific cation exchanged materials. Some exchanged materials are given in Part 1 already, and there are a few terms (i.e., mineral group names) that are listed in both Part 1 and Part 2. There are approximated 650 entries in Part 2. To be complete, any natural material is included that would be commonly found in a clay-related publication. Therefore, not only phyllosilicates and zeolites are included, but also manganese oxides, the astrophyllite group, double metal hydroxides, etc.
S. Guggenheim
CMS Nomenclature Committee Chair
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Steve Guggenheim, Professor Emeritus
Department of Earth and Environmental Sciences, m/c 186
University of Illinois at Chicago
845 W. Taylor St., Room 2440 SES
Chicago, Illinois 60607-7059
E-mail: xtal at uic.edu
Homepage: http://www.uic.edu/depts/geos/people/guggenheim_research.html
Phone: 312-996-3263
FAX: 312-413-2279
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From schroe at uga.edu Thu Apr 26 12:17:36 2018
From: schroe at uga.edu (Paul A Schroeder)
Date: Thu, 26 Apr 2018 16:17:36 +0000
Subject: [Clay-talk] Soil Clays from the SE United States
Message-ID: <9ED13119-96DC-40C7-8970-9DACC1AFABFD@uga.edu>
I am examining a soil feature where alternating paired red- and cream-colored layers occur about 1 meter below the surface in an Ultisol located in the SE United States. The parent rock (I think?) is an amphibolite-gneiss. The paired red- and cream layers are quasi-horizontal and alternate on about 1 to 2 cm thick intervals. Layers were carefully separated into ?red? and ?cream? samples (with a third sample representing the interface? i.e., likely a mixture of the two). Some pedologist might refer to the red/cream pattern a redoxiomorphic.
XRD analysis of oriented <2 ?m fraction air-dried slurry slides shows the expected kaolin group 00l reflections one would find in an Ultisol. Upon ethylene glycol saturation, the red sample displays peaks at 7.83? and 3.89?. Heating the red sample to 110?C and the 7.83?/3.89? phase remains. Heating to 360?C the 7.83?/3.89? phase disappears and a 3.368? phase appears. Heating to 550?C the kaolin phase and the 3.368? phase disappear and a 3.672? phase appears.
The 7.83?/3.89? phase matches well with apophyllite, which is known to thermally break down its structural water in two steps at ~260?C and ~450?C (therefore consistent with the structural changes seen in my heating experiments). There is one published description of apophyllite occurrence in an amphibole gneiss in Jackson, NC (about 200 km to the north in similarly aged and lithologic terrain), but my literature searches are not turning up much in the way of apophyllite in Ultisol settings.
Anyone come across a similar scenario?
Am I just missing an alternate XRD interpretation for the 7.83?/3.89? phase?
Paul Schroeder
Professor
Department of Geology
210 Field Street
University of Georgia
Athens, GA 30602-2501 USA
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